(function () {
  // Minimal event-handling wrapper.
  function stopEvent() {
    if (this.preventDefault) {
      this.preventDefault();
      this.stopPropagation();
    }
    else {
      this.returnValue = false;
      this.cancelBubble = true;
    }
  }

  function addStop(event) {
    if (!event.stop) event.stop = stopEvent;
    return event;
  }

  function connect(node, type, handler) {
    function wrapHandler(event) {
      handler(addStop(event || window.event));
    }

    if (typeof node.addEventListener == "function")
      node.addEventListener(type, wrapHandler, false);
    else
      node.attachEvent("on" + type, wrapHandler);
  }

  function forEach(arr, f) {
    for (var i = 0, e = arr.length; i < e; ++i) f(arr[i]);
  }

  var editor = CodeMirror.fromTextArea(document.getElementById("code"), {
    lineNumbers:true,
    theme:"night",
    onKeyEvent:function (i, e) {
      // Hook into ctrl-space
      if (e.keyCode == 32 && (e.ctrlKey || e.metaKey) && !e.altKey) {
        e.stop();
        return startComplete();
      }
    }
  });

  function startComplete() {
    // We want a single cursor position.
    if (editor.somethingSelected()) return;
    // Find the token at the cursor
    var cur = editor.getCursor(false), token = editor.getTokenAt(cur), tprop = token;
    // If it's not a 'word-style' token, ignore the token.
    if (!/^[\w$_]*$/.test(token.string)) {
      token = tprop = {start:cur.ch, end:cur.ch, string:"", state:token.state,
        className:token.string == "." ? "property" : null};
    }
    // If it is a property, find out what it is a property of.
    while (tprop.className == "property") {
      tprop = editor.getTokenAt({line:cur.line, ch:tprop.start});
      if (tprop.string != ".") return;
      tprop = editor.getTokenAt({line:cur.line, ch:tprop.start});
      if (!context) var context = [];
      context.push(tprop);
    }
    var completions = getCompletions(token, context);
    if (!completions.length) return;
    function insert(str) {
      editor.replaceRange(str, {line:cur.line, ch:token.start}, {line:cur.line, ch:token.end});
    }

    // When there is only one completion, use it directly.
    if (completions.length == 1) {
      insert(completions[0]);
      return true;
    }

    // Build the select widget
    var complete = document.createElement("div");
    complete.className = "completions";
    var sel = complete.appendChild(document.createElement("select"));
    // Opera doesn't move the selection when pressing up/down in a
    // multi-select, but it does properly support the size property on
    // single-selects, so no multi-select is necessary.
    if (!window.opera) sel.multiple = true;
    for (var i = 0; i < completions.length; ++i) {
      var opt = sel.appendChild(document.createElement("option"));
      opt.appendChild(document.createTextNode(completions[i]));
    }
    sel.firstChild.selected = true;
    sel.size = Math.min(10, completions.length);
    var pos = editor.cursorCoords();
    complete.style.left = pos.x + "px";
    complete.style.top = pos.yBot + "px";
    document.body.appendChild(complete);
    // Hack to hide the scrollbar.
    if (completions.length <= 10)
      complete.style.width = (sel.clientWidth - 1) + "px";

    var done = false;

    function close() {
      if (done) return;
      done = true;
      complete.parentNode.removeChild(complete);
    }

    function pick() {
      insert(sel.options[sel.selectedIndex].text);
      close();
      setTimeout(function () {
        editor.focus();
      }, 50);
    }

    connect(sel, "blur", close);
    connect(sel, "keydown", function (event) {
      var code = event.keyCode;
      // Enter and space
      if (code == 13 || code == 32) {
        event.stop();
        pick();
      }
      // Escape
      else if (code == 27) {
        event.stop();
        close();
        editor.focus();
      }
      else if (code != 38 && code != 40) {
        close();
        editor.focus();
        setTimeout(startComplete, 50);
      }
    });
    connect(sel, "dblclick", pick);

    sel.focus();
    // Opera sometimes ignores focusing a freshly created node
    if (window.opera) setTimeout(function () {
      if (!done) sel.focus();
    }, 100);
    return true;
  }

  var stringProps = ("charAt charCodeAt indexOf lastIndexOf substring substr slice trim trimLeft trimRight " +
    "toUpperCase toLowerCase split concat match replace search").split(" ");
  var arrayProps = ("length concat join splice push pop shift unshift slice reverse sort indexOf " +
    "lastIndexOf every some filter forEach map reduce reduceRight ").split(" ");
  var funcProps = "prototype apply call bind".split(" ");
  var keywords = ("break case catch continue debugger default delete do else false finally for function " +
    "if in instanceof new null return switch throw true try typeof var void while with").split(" ");

  function getCompletions(token, context) {
    var found = [], start = token.string;

    function maybeAdd(str) {
      if (str.indexOf(start) == 0) found.push(str);
    }

    function gatherCompletions(obj) {
      if (typeof obj == "string") forEach(stringProps, maybeAdd);
      else if (obj instanceof Array) forEach(arrayProps, maybeAdd);
      else if (obj instanceof Function) forEach(funcProps, maybeAdd);
      for (var name in obj) maybeAdd(name);
    }

    if (context) {
      // If this is a property, see if it belongs to some object we can
      // find in the current environment.
      var obj = context.pop(), base;
      if (obj.className == "variable")
        base = window[obj.string];
      else if (obj.className == "string")
        base = "";
      else if (obj.className == "atom")
        base = 1;
      while (base != null && context.length)
        base = base[context.pop().string];
      if (base != null) gatherCompletions(base);
    }
    else {
      // If not, just look in the window object and any local scope
      // (reading into JS mode internals to get at the local variables)
      for (var v = token.state.localVars; v; v = v.next) maybeAdd(v.name);
      gatherCompletions(window);
      forEach(keywords, maybeAdd);
    }
    return found;
  }
})();
